Re: Chromium sandbox on LoongArch and statx -- seccomp deep argument inspection again?

From: Xi Ruoyao <xry111@xry111.site>
To: Christian Brauner <brauner@kernel.org>, Arnd Bergmann <arnd@arndb.de>
Cc: Icenowy Zheng <uwu@icenowy.me>,
	Huacai Chen <chenhuacai@kernel.org>,
	 WANG Xuerui <kernel@xen0n.name>,
	linux-api@vger.kernel.org, Kees Cook <keescook@chromium.org>,
	Xuefeng Li <lixuefeng@loongson.cn>,
	Jianmin Lv <lvjianmin@loongson.cn>,
	Xiaotian Wu <wuxiaotian@loongson.cn>,
	WANG Rui <wangrui@loongson.cn>,
	Miao Wang <shankerwangmiao@gmail.com>,
	"loongarch@lists.linux.dev" <loongarch@lists.linux.dev>,
	Linux-Arch <linux-arch@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Chromium sandbox on LoongArch and statx -- seccomp deep argument inspection again?
Date: Tue, 27 Feb 2024 00:49:51 +0800	[thread overview]
Message-ID: <8e5e31daa3b76dc80ff5ec6ad46191bfd87f7df7.camel@xry111.site> (raw)
In-Reply-To: <20240226-sandbank-bewerben-219120323e29@brauner>

On Mon, 2024-02-26 at 16:40 +0100, Christian Brauner wrote:

> > I definitely don't want to see a new time32 API added to
> > mips64 and the 32-bit architectures, so the existing stat64
> > interface won't work as a statx replacement.
> 
> I don't specifically care but the same way you don't want to see newer
> time32 apis added to architectures I don't want to have hacks in our
> system calls that aren't even a clear solution to the problem outlined
> in this thread.

So we should have a fstat_whatever64, IMO.

> Short of adding fstatx() the problem isn't solved by a new flag to
> statx() as explained in my other mails. But I'm probably missing
> something here because I find this notion of "design system calls for
> seccomp and the Chromium sandbox" to be an absurd notion and it makes me
> a bit impatient.

I'm sharing the feeling on seccomp and/or (mis)uses of it, but using
statx() or fstatat() for fstat() has a performance impact as they must
inspect path (do a uaccess) and make sure it's an empty string, and
Linus concluded "if the user want fstat, you should give the user fstat"
for this issue:

https://sourceware.org/pipermail/libc-alpha/2023-September/151365.html

If it was just seccomp I'd not comment on this topic at all.

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University